An example of technologies that perform non-destructive inspection of the state of a welded portion and the state of a weld defect of a joined area between plate-like structures, an object to be inspected, is an ultrasonic test technology. In an ultrasonic inspection apparatus which adopts the ultrasonic test technology, the ultrasonic waves are irradiated to the welded area of the object to be inspected, and then are reflected from the welded area of the object to be inspected as echoes of the ultrasonic wave. After the reflected echoes of the ultrasonic wave are performed an imaging process, the ultrasonic inspection apparatus displays the reflected echoes performed the imaging process as an ultrasonic wave image, on the display device. The non-destructive inspection a state of the welded area or the weld defect is performed and thereby the user visually determines whether a state of the welded area or the weld defect is sound or not based on the ultrasonic wave image of the welded area.
Specifically, as described in Japanese Unexamined Patent Application Publication No. 11-326287 (Patent Document 1), when a plate-like structure is the object to be inspected, and two plate-like structures are superposed and joined together by means of spot welding, by inspecting the states of the welded portion between the two plate-like structures and a weld defect using the ultrasonic inspection apparatus, in a non-destructive manner, it is possible to inspect whether a molten-solidified portion exists in the welded portion or not, and the presence or absence of the weld defect such as a blowhole, and the state of the weld defect.
Further, as the inspection accuracy of the three-dimensional ultrasonic inspection apparatus constantly improves (increases), the three-dimensional ultrasonic inspection apparatus becomes possible to accurately and quantitatively determinate the state such as the layer structure, the weld defect in the object to be inspected, the presence or absence of the void or the separation, or the likes, of the welded area with respect to the object to be inspected. For example, the three-dimensional ultrasonic inspection apparatus disclosed in Japanese Published Unexamined Patent Application (Patent Laid-Open) No. 2005-315582 (Patent Document 2) inspects the positional relationship of the welded portion with respect to the object to be inspected, correctly, accurately and quantitatively in three dimensions.
Patent Document 1 is Published Unexamined Patent Application (Patent Laid-Open) No. 11-326287 (JP-A-11-326287); and
Patent Document 2 is Japanese Published Unexamined Patent Application (Patent Laid-Open) No. 2005-315582 (JP-A-2005-315582).
However, in case of the known three-dimensional ultrasonic inspection apparatus as described in the Patent Document 2, the state of the joined area displayed in the three-dimensional image of the joined area (the joined area image) is not always displayed in a state where the user can easily determine whether the state of the joined area is sound or not. Further, each transmitting image such as the transmitting images of the intermediate portion, the bottom portion or the likes is sliced at the z coordinate being same distance in z direction from each position (x, y) on the surface of object to be inspected. Thus, for example, if a situation that the probe leans a little occurs due to the shape of the object to be inspected or the likes, the intermediate portion or the bottom portion of the object to be inspected is obliquely sliced. Therefore, in this example case, even if the user views (checks) the joined area image, it is difficult for the user to correctly determine whether the state of the joined area is sound or not. Thus, in the method, for obtaining the transmitting image, adopted in the known three-dimensional ultrasonic inspection apparatus as described above, the accuracy of inspecting the joined area may be decreased.
In consideration of above circumstance, an object of the present invention is to provide a three-dimensional ultrasonic inspection apparatus improving easiness and visibility (obviousness) of determining whether the state of joined area is sound or not in comparison to the known ultrasonic inspection apparatus and further improving the inspection accuracy of the joined area because of being possible to obtain precise inspection result of the joined area.
The above mentioned objects can be achieved according to the present invention by providing, in one aspect, a three-dimensional ultrasonic inspection apparatus comprising:
an ultrasonic transducer in which a plurality of piezoelectric vibrators are disposed in a matrix or an array;
a driving element selecting device to sequentially select piezoelectric vibrators from the plurality of piezoelectric vibrators disposed in the ultrasonic transducer to produce an ultrasonic wave;
a signal detecting device to cause the ultrasonic wave generated by the piezoelectric vibrator selected by the drive element selecting device to propagate through an acoustic wave propagating medium and enter a joined area of an object to be inspected for receiving a reflected echo from the joined area, and to detect an electric signal corresponding to the reflected echo from the joined area;
a signal processing device to subject the electric signal detected by the signal detecting device to signal processing, and to generate three-dimensional imaging data by causing the electric signal to correspond to a mesh element partitioned in a three-dimensional imaging region set inside the object to be inspected; and
a display processing device to display a result of processing three-dimensional imaging data generated by the signal processing device,
wherein the display processing device includes:                a first peak detecting unit to detect a first peak of the intensity distribution of the three-dimensional imaging data in depth direction (z direction), the first peak primarily appearing at a depth position being deeper than a reference depth;        a second peak detecting unit to detect a second peak of the intensity distribution of the three-dimensional imaging data in depth direction, the second peak primarily appearing at a depth position being deeper than the depth position at which the first peak appears;        a joint portion image creation unit to create a three-dimensional image of a joined area by mapping a distance, between the depth position at which the first peak appears and the depth position at which the second peak appears, in depth direction at each position on x-y plane;        a determination unit to determine whether the joined area is sound or not in accordance with the three-dimensional image of the joined area, created by the joint portion image creation unit and a preset determination criteria; and        a display unit to display at least one of the three-dimensional image and the determination result determined by the determination unit.        
The three-dimensional ultrasonic inspection apparatus according to the present invention can make increased visibility determining whether the state of joined area is sound or not in comparison to the known ultrasonic inspection apparatus then provide the state of joined area, determined on the basis of the three-dimensional image of the joined area to user. Further, since the three-dimensional ultrasonic inspection apparatus according to the present invention can display the determination result whether the state of joined area is sound or not together with the three-dimensional image of the joined area, the three-dimensional ultrasonic inspection apparatus according to the present invention can provide more accurate inspection result to user. Furthermore, in the three-dimensional ultrasonic inspection apparatus according to the present invention, since an accuracy of the determination result whether the state of joined area is sound or not can be increased in comparison to the known ultrasonic inspection apparatus, an accuracy of the three-dimensional ultrasonic inspection can be also increased.